Investigation of Coal Wettability for the CO2 …...• Rock wettability, on the other hand, depends...
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Investigation of Coal Wettability for the CO 2 Sequestration and ECBM Applications: A Review Ahmed Ibrahim Texas A&M University
Transcript of Investigation of Coal Wettability for the CO2 …...• Rock wettability, on the other hand, depends...
Investigation of Coal Wettability for the CO2 Sequestration and ECBM
Applications: A Review
Ahmed IbrahimTexas A&M University
Outline
• Introduction• Experimental tools• Results
Effect of pressure Effect of coal rank Effect of water salinity Effect of temperature Effect of gas impurities
• Summary
Introduction
Coal is a complex organic rock and is often classified by rank.
lignite, subbituminous coal, bituminous coal, and anthracite
Ash Content,
Example for Coal Characterization
Element C O Al Si S Ca FeConcentration,
wt%82 10 0.8 0.44 2.53 0.25 2.23
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Composition of the coal.
Component Moisture Volatile Mater Fixed Carbon AshConcentration,
wt%0.2 47 50.8 2
Proximate analysis for the coal sample.
The coal sample was characterized as a high-volatile A bitumen coal (hvAb) (ASTM D388).
Introduction
• Coal is characterized by its dual porosity; matrix pore systemand cleats network system.
• CO sequestration in coal :1. Enhances methane production from coalbeds (ECBM). 2. Reduces the effect of global warming by storing CO .
• CO can be Stored in coal by three mechanisms: 1. Free gas within the cleats network system in coal;2. Adsorbed molecules on the organic surface of coal; and 3. Dissolved in groundwater within the coal.
Wettability Investigation
• The efficiency of ECBM and CO2 sequestration is strongly dependent on the wetting behavior of the coal–water–COsystem.
• If the coal is CO wet. CO2 will fill the micro-pores CO diffusion rate from the cleat network, through the micro-cleats, to
the matrix surface, will improved. ( improve replacement of the methane on the surface)
diffusion coefficient of CO2 = 1.7 10-7 m2/s at 100 bar and 300 K
diffusion coefficient of CO2 = 2 10-9 m2/s at 100 bar and 300 K (diffusion through water)
Experimental Tools
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Wet
tabi
lity
Inve
stig
atio
nW
etta
bilit
y In
vest
igat
ion Contact Angle Measurements Contact Angle Measurements
Zeta Potential measurementsZeta Potential measurements
Adsorption isotherm measurements Adsorption isotherm measurements
Fourier-transform infrared spectroscopy (FTIR)Fourier-transform infrared spectroscopy (FTIR)
Sessile Drop
Captive Bubble
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Wet
tabi
lity
Inve
stig
atio
nW
etta
bilit
y In
vest
igat
ion Contact Angle Measurements Contact Angle Measurements
Captive-bubble method is more represent the CO2 sequestration process, where the CO2displaces the water from the coal surface.
Contact Angle Measurements
• The Contact angle characterize the wetting behavior of the solid surface. < 90° Water wet > 90° CO2 wet
cos 𝜃 ,
where 𝜃 is the contact angle measured in the liquid, 𝛾 is thegas/solid interfacial tension, 𝛾 is the liquid/solid interfacial tension,and 𝛾 is the gas/liquid interfacial tension.
Zeta Potential Measurements
• Zeta potential can be measured for dispersions, and double layer thickness can be calculated from it.
• Rock wettability, on the other hand, depends on the stability of the water layer surrounding the rock surface, which is a function of the zeta potential.
• Zeta potential technique will be used to explain the causes of wettability alteration.
Zeta Potential Measurements
Higher Zeta Potential
Thicker and more stable
hydrated water layer
More hydrophilic
the rock
Adsorption Isotherm Measurements
• Adsorption isotherm aims to measure the adsorbed gas volume as function of pressure at constant temperature
• Most coal follows Langmuir adsorption behavior
𝐕𝐚𝐝𝐬𝐨𝐫𝐛𝐞𝐝𝐕𝐋𝐏
𝐏 𝐏𝐋.
y = 0.0492x + 61.4
y = 0.0121x + 99.6
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50
70
90
110
130
150
170
0 500 1000 1500 2000
Contact A
ngle, D
egree
Pressure, psi
hvBb_ Shojai et al. (2012) Semi anthracite_ Shojai et al. (2012)
Anthracitic_Siemons et al. (2006) hvAb_Present work
Semi anthracite_Arif et al. (2016) Lignite_Arif et al. (2016)
medium volatile bituminous_Arif et al. (2016)
Wettability Results
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Effect of Pressure on Contact angle Measurements
y = 0.0492x + 61.4
y = 0.0121x + 99.6
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50
70
90
110
130
150
170
0 500 1000 1500 2000
Contact A
ngle, D
egree
Pressure, psi
hvAb_Present work
DI water40°C
Discussion
• As the pressure increase
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2. The solubility of CO2 in water increased
1. CO2 adsorption on the coal surface increases at high pressure.
Gas interfacial tension to the solid 𝛾 ) decreased significantly
𝐶𝐴 cos 1𝛾 𝛾
𝛾
Effect of Pressure
pH decreased1
Destabilizes the water film on coal surface, and the coal becomes more hydrophobic2
𝛾 , 𝛾 , and 𝛾 are the gas/solid, the liquid/solid,and the gas/liquid interfacial tensions
1 Farokhpoor et al. 20132 Chiquet et al. 2007
0
200
400
600
800
1000
1200
1400
0 200 400 600 800 1000 1200 1400
Adsorbed
Gas Volum
e, scf/ton
Equilibrium Pressure, psi
DI (Langmuir equation)10 NaCl g/l (Langmuir equation)20 NaCl g/l (Langmuir equation)DI (Experimental Results)10 NaCl g/l (Experimental Results)20 NaCl g/l (Experimental Results)
3.7
3.75
3.8
3.85
3.9
3.95
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4.05
4.1
4.15
4.2
0
40
80
120
160
200
0 500 1000 1500 2000pH
CO2So
lubility, scf/STB
Pressure, psi
DI 2 wt%
pH_Di pH_2 wt%
Effect of Coal Rank
y = 0.0492x + 61.4
y = 0.0121x + 99.6
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50
70
90
110
130
150
170
0 500 1000 1500 2000
Contact A
ngle,
Degree
Pressure, psi
hvBb_ Shojai et al. (2012) Semi anthracite_ Shojai et al. (2012)
Anthracitic_Siemons et al. (2006) hvAb_Ibrahim and Nasr‐El‐Din (2016)
Semi anthracite_Arif et al. (2016) Lignite_Arif et al. (2016)
medium volatile bituminous_Arif et al. (2016)
Effect of Coal Rank
Chen et al. 2011
Sample 1
Sample 1Sample 2
Sample 2
Effect of Coal Rank
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Arif et al. 2017
Effect of Coal Rank
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Wavenumber Group
3690-3620 -OH group
910-1040 Si-O-Si
2925-1455 CH2
2850 CH3
700-900 C = C
High Rank Coal
High Rank Coal
Medium Rank CoalLow Rank Coal
Low Rank Coal
Effect of Coal Rank
Coal Rank
Oxygen –Containing GroupsCarbon Content
Coal Hydrophobicity
CO2 Coal Wettability
Effect of Water Salinity
• Coal-seam water usually has low salinity and varies between 800 to 28000 ppm.
Location TDS mg/L
Australia Bowen Basin Durham Ranch 5968
Fairview 1201Upper seam 6207Lower seam 6528
US
Black Warrior Basin 4402San Juan Basin 28783
Uinta Basin 11876Maramarua 837
Salinity of Coal Seam Associated Water (Hamawand et al., 2013).
Effect of Water Salinity
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70
80
90
100
110
120
130
0 500 1000 1500 2000
Contact A
ngle , De
gree
Cell Pressure, psi
20 g/L NaCl Brine10 g/L NaCl BrineDI Water
hvAb coal sample at 40 C
Ibrahim 2016Arif et al. 2017
Effect of Water Salinity
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0
200
400
600
800
1000
1200
1400
0 200 400 600 800 1000 1200 1400
Adsorbed
Gas Vo
lume,
scf/t
on
Equilibrium Pressure, psi
DI (Langmuir equation)10 NaCl g/l (Langmuir equation)20 NaCl g/l (Langmuir equation)DI (Experimental Results)10 NaCl g/l (Experimental Results)20 NaCl g/l (Experimental Results)
(40℃)
y = 1329.17x - 413.08R² = 0.9991
y = 1788.13x - 566.44R² = 0.9931
y = 1492.03x - 423.93R² = 0.9941
0
300
600
900
0.3 0.5 0.7 0.9
Equil
ibrium
Pres
sure,
psi
Equilibrium Pressure/Adsorbed Gas Volume
𝐏 𝐕𝐋 𝐏
𝐕𝐚𝐝𝐬𝐨𝐫𝐛𝐞𝐝𝐏𝐋
PL Langmuir adsorption pressure, psiVL Langmuir adsorption volume, scf/ton
Effect of Water Salinity
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Discussion
• As the salinity increase
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1. CO2 adsorption on the coal surface increases
Gas interfacial tension to the solid 𝛾 ) decreased significantly
𝐶𝐴 cos 1𝛾 𝛾
𝛾
Effect of Salinity
2. It compresses and destabilizes the hydrated layers (double layer) surrounding the coal surface, causing a reduction in the absolute value of the zeta potential, and making the coal surface more hydrophobic.
Effect of Temperature
As the temperature increases;• Gas adsorption decreases• Surface oxidization increases
Effect of Gas Composition
Summary
• CO2 can be sequestrated in coal seams to enhance the coalbed methane production (ECBM) in addition to CO2 storage. The efficiency of this process greatly affected by the coal formation properties and the operation conditions as following;
1. As the coal rank increased from lignite to anthracite, gas adsorption capacity increases and the coal become morehydrophobic.
2. With increasing pressure, coal became more hydrophobicas a result of lower pH value and high CO2 adsorption.
3. Adsorption capability decreases and the coal becomes more water-wet at high formation temperature.
Summary
4. As the formation water salinity increases, the coal becomes more gas-wet and the adsorption isotherm increases.
5. The presence of N2 in the injected gas decreases the coal wettability to gas.
For carbon sequestration and ECBM application, the storage capacity of CO2 in coal increased as the formation water salinity, coal rank, and the formation pressure increased. The gas storage as free gas increases, where the displacement efficiency increases as the coal become more CO2 wet. Also, the adsorbed gas phase increases due to the CO2 adsorption isotherm increase.
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Investigation of Coal Wettability for the CO2 Sequestration and ECBM Applications: A Review
Thank YouQuestions
Coal Rank
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